The make-up water supply for future steam-assisted production is an area of critical concern. There is an ecological push for fresh or “non-saline” water to not be used but instead to use saline water; however typically saline water contains a high amount of total dissolved solids. The costs associated with treating a water stream with a high amount of dissolved solids can be very expensive.
Water recovery by condensation from commercial-size boiler flue gas streams is an idea that has been discussed for quite some time. Many industrial processes produce process streams containing condensable components such as water vapor. As the mere discarding of these condensable components can constitute a substantial loss in available heat energy, it is desirable to recover these condensable components from the process streams for economic reasons. It is also desirable to recover the latent heat of vaporization associated with such condensable components as a means for reducing process energy requirements. The use of heat exchanger-based condensers for the recovery of condensable components of process streams and the latent heat of vaporization associated therewith is well known to those skilled in the art.
Methods and apparatuses for the selective removal of one or more components from a gaseous mixture are well known. U.S. Pat. No. 4,875,908 teaches a process for selectively separating water vapor from a multi-component gaseous mixture in which the multi-component gaseous mixture comprising the water vapor is passed along and in contact with a membrane which is selectively permeable to water vapor. The use of membranes for selective removal of one or more components of a gaseous mixture is also taught by U.S. Pat. No. 4,583,996 (inorganic porous membrane), U.S. Pat. No. 3,980,605 (fibrous semi-permeable membrane) and U.S. Pat. No. 3,735,559 (sulfonated polyxylylene oxide membranes).
Methods and apparatuses for selective removal of water vapor from a gaseous mixture and condensing the separated water vapor to recover its latent heat of vaporization are also known. U.S. Pat. No. 5,236,474 teaches a process for removing and recovering a condensable vapor from a gas stream by a membrane contactor in which a gas stream containing a condensable vapor is circulated on one side of hollow fiber membranes while cool extraction fluid is circulated on the other side under a total pressure differential. As a result, the condensable vapor in the gas stream is condensed in the gas stream and the condensed vapor, i.e. liquid, permeates the membrane and becomes entrained in the cool extraction fluid.
U.S. Pat. No. 4,466,202 teaches a process for recovery and reuse of heat contained in the wet exhaust gases emanating from a solids dryer or liquor concentrator by preferentially passing the vapor through a semi-permeable membrane, compressing the water or solvent vapor, and subsequently condensing the water or soluble vapor in a heat exchanger, thereby permitting recovery of its latent heat of vaporization for reuse in the evaporation process. It will be apparent to those skilled in the art that a substantial amount of energy will be required to compress the water or solvent vapor in accordance with the process of this patent. U.S. Pat. No. 5,071,451 teaches a vapor recovery system and process that permits condenser vent gas to be recirculated. The system includes a small auxiliary membrane module or set of modules installed across a pump and condenser on the downstream side of a main membrane unit, which module takes as its feed the vent gas from the condenser and returns a vapor-enriched stream upstream of the pump and condenser.
U.S. Pat. No. 7,066,396 teaches a heating system having a steam generator or water heater, at least one economizer, at least one condenser and at least one oxidant heater arranged in a manner so as to reduce the temperature and humidity of the exhaust gas stream and recover a major portion of the associated sensible and latent heat. The recovered heat is returned to the steam generator or water heater so as to increase the quantity of steam generated or water heated per quantity of fuel consumed. In addition, a portion of the water vapor produced by combustion of fuel is reclaimed for use as feed water, thereby reducing the make up water requirement for the system. However, U.S. Pat. No. 7,066,396 provides no teaching or suggestion of producing make-up water for a steam-assisted production system while cleaning and neutralizing the flue gas prior to the heat recovery.
U.S. Pat. No. 4,799,941 teaches a method for condensing flue gas in combustion plants, and an arrangement of the apparatus herefor. U.S. Pat. No. 4,799,941 attempts to condense flue gas in combustion plants by: (a) cooling and humidifying the flue gas by spraying water thereinto; (b) cooling and condensing water vapor from the flue gases in a first condensing stage, by indirect heat exchange with recirculated water, or return water, from a hot water circuit; (c) further cooling and condensing water vapor from the flue gases in a second condensing stage, by indirect heat exchange with water from a combustion air humidifier; and (d) heating and humidifying combustion air in the humidifier by direct contact with heated recirculated water from the second condensing stage. However, U.S. Pat. No. 4,799,941 provides no teaching or suggestion of producing make-up water during a steam-assisted production while cleaning and neutralizing the flue gas prior to the heat recovery.